8 June 2009
The idea of the Hawthorne effect is that individuals may change their behavior because they are being studied, in addition to any real effects of the intervention. Steven Levitt and John List have revisited the illumination experiments at the Hawthorne plant that gave name to the effect, and argue that many of the original conclusions do not hold up to scrutiny. There's an Economist article on the paper here but its subtitle "Being watched may not affect behavior, after all" is misleading: even if the earlier research was sloppy by today's standards the contribution was to point out the possibility of these effects. A better subtitle could have commended replication as important scientific method.
Levitt and List (2009) "Was there Really a Hawthorne Effect at the Hawthorne Plant? An Analysis of the Original Illumination Experiments" NBER Working Paper #15016, http://www.nber.org/papers/w15016.pdf
The Economist (June 4, 2009) "Light work: Questioning the Hawthorne effect", http://www.economist.com/finance/displayStory.cfm?story_id=13788427